Method of and means for translating sound waves



Nov. 2 1926.

E. SHRADER METHOD OF AND MEANS FOR TRANSLATI NG SOUND WAVES Filed 02m.11, 1922 Fig INVENTOR James E. Shmdev.

WITNESSES:

/ ATTORNEY Patented Nov. 2, 1926.

UNITED STATES 1,605,295 PATENT OFFICE.

JAMES 'E. SHRADER, 0F EDGEWOOD, PENNSYLVANIA, ASSIGNOR TO WESTINGHOUSEELECTRIC & MANUFACTURING COMPANY, A CORPORATION OF PENNSYLVANIA.

METHOD OF .AND MEANS FOR TRANSLATING SOUND WAVES.

Application filed October 11, 1922. Serial No. 598,682.

My invention relates to telephone systems and apparatus and particularlyto soundwave translating device of an improved type. z y

6 In its broad aspect, an object of my invention is to provide asoundnvave translating device and a .cir'cuitarrangement therefor,whereby sound waves may be faithfully translated into correspondinglymodulated electrical energy without impairing the quality, tone and,quantity of the translated energy. v z 1 More specifically, an object ofmy invention is to provide a translating device which.

is operable inan atmosphere of air, which embodies no moving parts andwhich is further characterized .by itssimplicity of design, efficiencyof operation and lack of complicated adjustments, the several parts of 2which may be easily made by existing automatic machinery and may bereadily assembled with a minimum expenditure of time and of money. w z

The'ordinary sound-wave translating de- 2 vice known as a resistormicrophone of the carbon capsule type embodies certain inherentundesirable features well known to those skilled in the art, as, forinstance, the employment of a vibratory element which tends not only tointroduce distortion, but also to complicate the construction of thetransmitter.

In carrying my invention into practice, I provide a sound-wavetranslating device which is based upon the fact that the amount ofionization in an electrical dis charge contained in a gaseous medium isdetermined by the pressure of the medium.

In one form of my invention, the translating device comprises a pair ofspaced electrodes which are coated --with a radioactive materialemitting ionizing radiations and which are shunted by an energy. sourceimpressing a potential thereacross of sufficient value to establish anionization space current. A repeater device of the threeelectrode typeis operatively associated with the translating device to convert thevariations in the intensity'of the ionization current with pressure intoamplified electrical currents of similar wave form. I

\Vith these and other objects and applications in view, myinvention'further consists in the nature, the mode of operation and thedetails of construction hereinafter described and claimed andillustrated in the drawing, I wherein:

Figure 1 is a diagrammatic-view of one embodiment of my invention;

Fig. 2 is a similar view of a modification. In one form of my mventlon,a soundwave translating device 1 is operatively associated with arepeater amplifying device 2, the latter serving to amplify the effectsof the former, all as hereinafter more fully tively lowionizationvoltage, as, for in- I stance, air. Adjacent surfaces of theelectrodes 3 and 4 are coatedwith a radio-active substance, 5? as, forinstance, uranium,

radium or thorium. Such substances are characterized by the fact thatthey are continuously emanating high-velocit electrical particles, whichsometimes take t e form ofalpha particles. Since the ionization voltageof the medium containing the electrodes 3 and 4 is low in'comparisonwith the veloc 89 ity of the particles, thespace intermediate the twoelectrodes 3 and 4 is continuouslym a state of ionization. 'The spaceintermediatethe two electrodes 3 and 4 may be rendered conducting byimpressing a-source 6 of direct-current energy ther'eacross' throughconductors 7 and 8, respectively. Since the amount of ionization, whichis produced by the rapidly moving charges emanating from theradio-active coatings 5 varies directly with the pressure of theatmosphereenveloping the same, it is seen that the effect of impressedsound waves upon the space-current path intermediate the pair ofelectrodes 3 and 4 is to corre- '95 spondingly vary the intensity of theionizing currents traversing the same. The modulated currents traversingthe circuit, connecting the electrodes 3 and 4 may be impressed upon theinput elements 9 and 11 1' of a repeater device 12 through'a couplingtransformer 13, the primary winding 14 of which may be included in theconductor8 while the secondary winding'15 of which is connected to theinput elements just mentioned.

A grid biasing condenser 16 having a negligible impedance to currents ofsound-wave frequency is included in the grid circuit while agrid-leak'resistor 17 is connected in with the pressure variations.

shunt relation to the grid and filament elements 9 and 11, in order tocontrol the intensity of the negative charges which are accumulated onthe grid 9 of the repeater device 12. The tube 12 is also provided withthe customary plate 18 and plate-filament circuit 19, the latterincluding a source 21 of directcurrent energy and a primary winding 22of a coupling transformer 23. A secondary winding 24 of the couplingtransformer 23 may be connected to the input elements of an amplifyingdevice (not shown) or other circuit arrangement employing such modulatedenergy.

\Vhen sound waves are impressed upon the space-current path between theelectrodes 3 and 4, the number of collisions between the high velocityparticles emanating from the electrodes 3 and 4 and the molecules of thegas contained in the space therebetween are correspondingly varied.Thus, the intensity of the ionizing currents traversing the spacecurrent path is .modulated in accordance The resulting modulatedalternating currents traversing the primary winding 14: of thetransformer 13 are impressed upon the inputelements 9 and 11 of therepeater device" 12 to cause greatly amplified currents of correspondingwave form to traverse the plate-filament cir cuit thereof. The amplifiedmodulated currents traversing the latter circuit may then be impressedupon other amplifying means (not shown) through the coupling transformer23, having a primary 22 and a secondary 24.

The arrangement shown in Fig. 2 is distinguished from that of Fig. v1 inthe design.

of the discharge electrodes of the translating device. In this figure,the electrodes 25'and 26 comprise a cylinder and a rod, respectively,with the latter disposed in the longitudinal axis of the former. As inFig. 1,

adjacent surfaces are coated with the radioactive material 5. Theoperation of this figure is the same as that of Fig. 1.

In operation, my apparatus provides a space-current path having avariable impedance resulting from differences in pressure at successiveinstants at any point in a propagated sound wave traversing the spacebetween two electrodes in the presence of an ionizing means. It will beobvious, therefore, that the dimensions of the space included betweenthe electrodes should preferably be small, in the direction ofpropagation of the sound, as compared with the shortest wavelength ofthe sound.

While I have shown and described a particular means for producing anionizing stream, as by radio-active substance, it is apparent that othermeans are applicable to my invention, as by thermal means, orphotoelectric means. Moreover, while I have described two specificembodiments of my invention for the purpose of illustrating itsprinciples of operation, various changes and modifications may be madetherein without departing from the spirit and scope of my invention. Idesire, therefore, that only such. limitations shall be imposed thereonas are indicated by the appended claim or demanded by the prior art.

I claim as my invention:

A sound-wave translating device comprising an electrical circuitincluding a spacecurrent path between two radio-active electrodes in theair, and means for amplifying the variations in an electrical quantityin said circuit resulting from sound waves in said space.

In testimony whereof, I have hereunto subscribed my name this fourth dayof October, 1922.

JAMES E. SHRADER.

